Highly uniform silicon carbide epitaxial layers

Abstract

An improved chemical vapor deposition method is disclosed that increases the uniformity of silicon carbide epitaxial layers and that is particularly useful for obtaining thicker epitaxial layers. The method comprises heating a reactor to a temperature at which silicon carbide source gases will form an epitaxial layer of silicon carbide on a substrate in the reactor; and then directing a flow of source and carrier gases through the heated reactor to form an epitaxial layer of silicon carbide on the substrate with the carrier gases comprising a blend of hydrogen and a second gas in which the second gas has a thermal conductivity that is less than the thermal conductivity of hydrogen so that the source gases deplete less as they pass through the reactor than they would if hydrogen is used as the sole carrier gas.

That which is claimed is:  
     
       1. A silicon carbide epitaxial layer having an epicrown along the outer perimeter of the layer, said layer having a standard deviation of thickness along its cross section of less than two percent excluding the data points measured on the epi-crown wherein the area of said layer is at least 4π mm 2 . 
     
     
       2. A silicon carbide epitaxial layer according to claim  1  on a single crystal silicon carbide substrate. 
     
     
       3. A silicon carbide epitaxial layer according to claim  2  wherein said silicon carbide substrate is selected from the group consisting of the 4H and 6H polytypes of silicon carbide. 
     
     
       4. A silicon carbide epitaxial layer according to claim  1  with a standard deviation of thickness across its cross section of less than 1 percent. 
     
     
       5. A silicon carbide epitaxial layer according to claim  4  on a single crystal silicon carbide substrate. 
     
     
       6. A silicon carbide epitaxial layer according to claim  5  wherein said silicon carbide substrate is selected from the group consisting of the 4H and 6H polytypes of silicon carbide.